Question

Patients who are extremely allergic to bee stings will self-administer epinephrine when stung. The activation of adrenergic beta-receptors by the injected epinephrine will decrease

a. The contraction of airway smooth muscle
b. The strength of ventricular muscle contraction
c. The rate of depolarization in the SA node
d. The transport of calcium into skeletal muscle fibers
e. The rate of glycogenolysis in the liver

Answer 1

Epinephrine activates adrenergic beta-receptors resulting in the relaxation of airway smooth muscle, which is essential for counteracting symptoms like airway constriction in anaphylactic reactions.

Step-by-step explanation:

When an individual with a severe allergy to bee stings is exposed to the allergen, the common therapeutic step is to self-administer epinephrine to counteract the symptoms of anaphylaxis. The activation of adrenergic beta-receptors by epinephrine, in particular, plays a crucial role in mitigating the adverse effects of a severe allergic reaction.

Epinephrine achieves this by various mechanisms, including:

1. Increasing the contraction of cardiac muscles (positive inotropic effect).
2. Increasing the heart rate by enhancing the rate of depolarization in the SA node (positive chronotropic effect).
3. Inducing the relaxation of airway smooth muscle, which helps to alleviate breathing difficulties during anaphylaxis.
4. Promoting glycogenolysis in the liver, which increases blood glucose levels to provide immediate energy in response to stress.

Given the physiological effects of epinephrine on the body, the correct answer to the question is:

a. The contraction of airway smooth muscle.

The activation of adrenergic beta-receptors by epinephrine will lead to the relaxation, not an increase in the contraction, of airway smooth muscle, helping to open the airways and allow better breathing. This is a crucial response to counteract the symptoms of anaphylaxis, which can include constriction of the airways leading to difficulty breathing.